This invention relates to a laser apparatus for selecting a laser light beam having a specific wavelength region among laser light beams having different wavelength regions.
In general, in many cases a laser device simultaneously oscillates laser light beams having a plurality of wavelength regions. In this event, a gas material is filled in an ion laser tube of the laser device (for example, a Krypton ion laser device or an argon ion laser device) and has a plurality of energy levels which are excited by discharge. Laser light beams having a plurality of wavelength regions are oscillated by amplification in accordance with a plurality of energy levels. The amplification is carried out by the use of a pair of optical resonance mirrors which are arranged opposite to each other via the ion laser tube. In this case, the light beam of the wavelength region to be oscillated is reflected to resonate between the pair of light resonance mirrors.
In the laser device (ion laser device) which oscillates the laser light beams having two or more wavelength regions, the laser light beam having a specific wavelength region is obtained from the ion laser device by adjusting reflection characteristics of the pair of resonance mirrors. Alternatively, the laser light beams having a plurality of wavelength regions which covers a wide wavelength region also may be obtained.
In addition, the laser light beams having different wavelength regions can be selectively obtained from the same ion laser device by switching a plurality of optical resonance mirrors corresponding to different wavelength regions.
It is useful to select different wavelength regions from a single laser device in the case of a medical care and applications of photosensitive and luminescence materials.
In this case, such a general concept that a specific wavelength region is selected by switching the mirrors is conventional in the laser apparatus which oscillates the laser light beams having two or more wavelength regions.
For example, a laser apparatus having two mirrors in a cradle, mounted via a bellows, inside a laser tube has been disclosed in U.S. Pat. No. 5,426,662 (reference 1). In such a laser apparatus, one mirror is selected from the two mirrors by switching the positions of the cradle.
On the other hand, another laser apparatus including a mirror mount having two mirrors outside a laser tube has been disclosed in Japanese Unexamined Utility Model Publication NO. S63-71563 (reference 2). In this laser device, one mirror is selected from the two mirrors by moving the mirror mount, like the reference 1.
However, the references 1 and 2 have the following defects. Namely, a structure for supporting the mirrors becomes complicated and heavy. Further, the oscillation inevitably halts when the mechanism for switching the positions of a mirror holder, such as the cradle and the mirror mount, fails. That is, because two mirrors are mounted to the same mirror holder, neither mirror may be positioned properly when the switching mechanisms fails.